Mid-infrared silicon photonics

A mid-infrared silicon nanophotonic integrated circuit platform can have broad impact upon environmental monitoring, personalized healthcare, and public safety applications. Development of various mid-IR components, including optical parametric amplifiers, sources, modulators, and detectors, is reviewed

Accurate Nanofabrication Techniques for High-Index-Contrast Microphotonic Devices

Thesis Supervisor: Henry I. Smith Title: Joseph F. and Nancy P. Keithley Professor of Electrical Engineering Thesis Supervisor: Harry L. Tuller Title: Professor of Ceramics and Electronic MaterialsHigh-refractive-index-contrast microphotonic devices provide strong light confinement allowing for sharp waveguide bends and small dielectric optical resonators. They allow dense optical integration and unique applications to optical filters and sensors but present exceptional complications in design and fabrication. In this work, nanofabrication techniques are developed to address the two main challenges in fabrication of high-indexcontrast microphotonic devices: sidewall roughness and dimensional accuracy. The work focuses on fabrication of optical add-drop filters based on high-indexcontrast microring-resonators. The fabrication is based on direct-write scanning-electronbeam lithography. A sidewall-roughness characterization and optimization scheme is developed as is the first three-dimensional analysis of scattering losses due to sidewall roughness. Writing strategy in scanning-electron-beam lithography and absolute and relative dimensional control are addressed. The nanofabrication techniques developed allowed fabrication of the most advanced microring add-drop-filters reported in the literature. The sidewall-roughness standarddeviation was reduced to 1.6 nm. The field polarization and the waveguide cross-sections minimizing scattering losses are presented. An absolute dimensional control accuracy of 5 nm is demonstrated. Microring resonators with average ring-waveguide widths matched to 26 pm to a desired relative width-offset are reported

Global design rules for silicon microphotonic waveguides: sensitivity, polarization and resonance tunability

Abstract: In a rigorous design study of silicon-in-silica waveguides and resonators we address critical parameters for tunable filters. 6:1 aspect-ratio TE and 2:1 TM waveguide designs optimize resonance-frequency dimensional tolerances, proximate metal-electrode loss and other constraints. High-index-contrast (HIC) microphotonic circuits employ strong index confinement to provide high Q's in small resonators with a free spectral range (FSR) in the 10's of nm. They enable widely tunable integrated add-drop filters for transparent optical networks In this paper, we investigate optimal designs of silica-clad silicon-core (Si) waveguides in terms of waveguide cross-section and field polarization, with respect to an extensive set of practically relevant criteria: sufficiently large feature sizes; low sensitivity of resonance frequencies and waveguide-cavity couplings to dimensional variations; high Q and large FSR; small propagation loss due to waveguide roughness; and efficient thermo-optic tuning. With a view toward thermally tunable high-order microring resonators, we find that dimensional sensitivity of the resonance frequency, and proximity of metallic heaters (causing optical absorption) ultimately determine the choice of design. The results give two very different optimal designs for the choice of TE or TM device operation (about 700x120nm and 480x260nm, respectively). In comparison, the Si waveguides typically employed for TE excitation (~450x200nm) are much more sensitive to dimensional error, rendering high-order filters difficult to realize. We parameterize our study throughout by waveguide aspect ratio (A R ), for designs using TE and TM excitation

Dynamical systems in nanophotonics: From energy efficient modulators to light forces and optomechanics

We demonstrate novel device concepts based on rigorous design of the dynamics of resonant nanophotonic systems, such as dispersionless resonant switches and energy-efficient mo-dulator architectures, slow-light cells, and nanomechanical photonic devices based on light forces

Flip-chip III-V-to-silicon photonics interfaces for optical sensor

We demonstrate flip-chip solder assembly of InP chips on Silicon-Photonic (Si-Ph) substrates aimed at high volume manufacturing using typical microelectronic lead-free solders. In our show-case application, an InP die is both a light source and a detector in an integrated optical methane gas sensor that operates near 1.6mm. For high-resolution laser absorption spectroscopy sensing, a single-mode tunable laser is desired. We create an external cavity laser with InP as optical gain, butt-coupled to a Si-Ph external cavity, which incorporates the laser's frequency selective elements. For minimal reflection at the InP-Si interface, waveguides are angled to the facet, an index-matching medium is applied between the mating surfaces, and an anti-reflection coating designed for the index-matching medium is applied to the optical coupling facet of InP chip. Sub-micron alignment accuracy is obtained without high-accuracy assembly tooling. Lithographically defined alignment features on both InP and Si components allow reproducible high-accuracy alignment. Interface throughput loss were measured to be as low as 1.4 dB, and interface reflections are more than 30dB smaller than main signal beams

Flip-chip III-V-to-silicon photonics interfaces for optical sensor

\u3cp\u3eWe demonstrate flip-chip solder assembly of InP chips on Silicon-Photonic (Si-Ph) substrates aimed at high volume manufacturing using typical microelectronic lead-free solders. In our show-case application, an InP die is both a light source and a detector in an integrated optical methane gas sensor that operates near 1.6mm. For high-resolution laser absorption spectroscopy sensing, a single-mode tunable laser is desired. We create an external cavity laser with InP as optical gain, butt-coupled to a Si-Ph external cavity, which incorporates the laser's frequency selective elements. For minimal reflection at the InP-Si interface, waveguides are angled to the facet, an index-matching medium is applied between the mating surfaces, and an anti-reflection coating designed for the index-matching medium is applied to the optical coupling facet of InP chip. Sub-micron alignment accuracy is obtained without high-accuracy assembly tooling. Lithographically defined alignment features on both InP and Si components allow reproducible high-accuracy alignment. Interface throughput loss were measured to be as low as 1.4 dB, and interface reflections are more than 30dB smaller than main signal beams.\u3c/p\u3